text: Tholins occur on the dwarf planet Pluto and are responsible for red colors as well as the blue tint of the atmosphere of Pluto. The reddish-brown cap of the north pole of Charon, the largest of five moons of Pluto, is thought to be composed of tholins, produced from methane, nitrogen and related gases released from the atmosphere of Pluto and transferred over about  distance to the orbiting moon.